Gradual Evolution from Fluvial Dominated to Tide Dominated Deltas and Channel Type Transformation: A Case Study of MPE3 Block in the Orinoco Heavy Oil Belt of the Eastern Venezuelan Basin  

作　　者：HUANG Wensong CHEN Heping XU Fang MENG Zheng ZHANG Fanqin WU Suwei 

机构地区：[1]PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China [2]University of Calgary,Canada

出　　处：《Acta Geologica Sinica(English Edition)》2019年第6期1909-1921,共13页地质学报（英文版）

基　　金：supported by the Important National Science Technology Specific Projects (number 2016ZX05031-001)

摘　　要：Based on the data of core description and sporopollen analysis,the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed by seismic phase and well logging facies interpretation.The results show that due to the great sea level rise,the sedimentary system of the Miocene Oficina Formation in the MPE3 block shifted from the distal-source sandy braided river delta to tide-affected delta,and eventually to tide-dominated delta.Vertically,during the early stage of sedimentation of Oficina Formation,the distributary channels of the delta were dominated by braided river channels.While in the later stage,as the tidal effect was gradually intensified,the channel changed from braided channel to meandering channel.On plane,as a result of differential transgression,sedimentary framework and distribution of sand bodies vary across the study area.Compared with the eastern part,the western part has more braided channels,larger channel bars,less developments of distributary bay and higher ratio of sand to mud.Whereas the braided channels in the south are larger than those in the north.It is the first time we pointed out the impact of marine transgression differences on the sedimentary facies distribution and river type transition in the study area.Factors like the structural and paleogeomorphological change,sea level variation,supply of sediments have strong influence on the evolution of sedimentary system and distribution of sandbodies.It is predicted that the major sandbody is more developed in the central south,which can guide the subsequent horizontal well development.Based on the data of core description and sporopollen analysis, the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed by seismic phase and well logging facies interpretation. The results show that due to the great sea level rise, the sedimentary system of the Miocene Oficina Formation in the MPE3 block shifted from the distal-source sandy braided river delta to tide-affected delta, and eventually to tide-dominated delta. Vertically, during the early stage of sedimentation of Oficina Formation, the distributary channels of the delta were dominated by braided river channels. While in the later stage, as the tidal effect was gradually intensified, the channel changed from braided channel to meandering channel. On plane, as a result of differential transgression, sedimentary framework and distribution of sand bodies vary across the study area. Compared with the eastern part, the western part has more braided channels, larger channel bars, less developments of distributary bay and higher ratio of sand to mud. Whereas the braided channels in the south are larger than those in the north. It is the first time we pointed out the impact of marine transgression differences on the sedimentary facies distribution and river type transition in the study area. Factors like the structural and paleogeomorphological change, sea level variation, supply of sediments have strong influence on the evolution of sedimentary system and distribution of sandbodies. It is predicted that the major sandbody is more developed in the central south, which can guide the subsequent horizontal well development.

关 键 词：Orinoco heavy oil belt Miocene Oficina Formation braided river-dominated delta tide-dominated delta river type transition 

分 类 号：P58[天文地球—岩石学]